1. Field of the Invention
The present invention relates to hydraulic brake bleeder apparatus for bleeding hydraulic brake fluid from a vehicle hydraulic brake system.
2. Description of the Prior Art
Vehicle hydraulic brake systems conventionally comprise a master cylinder and individual cylinders for each wheel. The master cylinder is connected to the brake cylinders by means of fluid lines. A special hydraulic brake fluid is used in the system. Occasionally, it happens that air bubbles become entrained in the hydraulic brake fluid. Such air bubbles affect the operational characteristics of the brake system. When the brake pedal is depressed, brake fluid is placed under pressure in the master cylinder and this pressure is communicated to each of the wheel brake cylinders. Communication of the pressure from the master cylinder to the brake cylinders is substantially instant and in direct proportion to the pressure applied to the master cylinder. However, when air is entrained in the hydraulic fluid of the system, it will be compressed upon an increase of fluid pressure in the brake system (it being appreciated that hydraulic brake fluid is a liquid which is substantially incompressible). Compression of the air results in reducing the brake pressure applied and also causing a time delay between application of pressure via the brake pedal and reflection of such pressure in the brake cylinders. The common remark is that a brake system having any substantial amount of entrapped air results in a "spongy" operation of the brake system.
The conventional method for correcting this problem is to bleed brake fluid from the system and thereby get rid of that portion of the brake fluid which has air entrapped therein.
This process is normally a two person job. It is necessary for one person to apply fluid pressure to the hydraulic brake system during the bleeding operation. This is accomplished either by one person applying pressure via the brake pedal or applying pressure by use of a manually-operated pressure apparatus. The second person controls the bleeding operation from a standpoint of drawing fluid from the system and watching the fluid to make sure that all fluid having air bubbles therein is extracted from the system. It is also necessary for this person to frequently check the fluid level of the master cylinder reservoir to be sure that adequate hydraulic brake fluid is present at all times.
In accordance with the present invention, brake bleeder pump means are actuated by a pneumatic motor, thus eliminating the need for one person to generate brake fluid pressure. Additionally, brake fluid is automatically supplied to the master cylinder reservoir by means of hydraulic brake fluid supply means attachable to the master cylinder reservoir, thus eliminating the need to check the level of fluid in the reservoir.